Fault current limiting superconducting coil

Abstract

A superconducting magnetic coil includes a first superconductor formed of an anisotropic superconducting material for providing a low-loss magnetic field characteristic for magnetic fields parallel to the longitudinal axis of the coil and a second superconductor having a low loss magnetic field characteristic for magnetic fields perpendicular to the longitudinal axis of the coil. The first superconductor has a normal state resistivity characteristic conducive for providing current limiting in the event that the superconducting magnetic coil is subjected to a current fault.

What is claimed is: 
     
       1. A superconducting magnetic coil assembly having a center section and two end sections positioned along a longitudinal axis for generating a magnetic field that varies along the longitudinal axis of the coil assembly, the coil assembly comprising: an anisotropic first superconductor wound about the longitudinal axis of the coil assembly in a region of the center section and forming a first coil section, the first superconductor having a first resistivity characteristic in a normal state of operation; and   a second superconductor wound about the longitudinal axis of the coil assembly in a region of at least one of the end sections and forming at least one second coil section, said second coil section connected in series to the first coil section, the second superconductor in a superconducting state of operation and in the presence of a magnetic field oriented perpendicular to the longitudinal axis, an AC loss characteristic of the second superconductor lower than an AC loss characteristic of the first superconductor, and   in a normal state of operation, a second resistivity characteristic of the second superconductor is less than the resistivity characteristic of the first anisotropic superconductor in a normal state of operation.   
     
     
       2. The superconducting magnetic coil of claim 1 wherein the second superconductor is connected to an end of the first anisotropic superconductor and is configured to provide a low AC loss characteristic in the presence of perpendicular magnetic fields. 
     
     
       3. The superconducting magnetic coil assembly of claim 1 wherein the second superconductor is formed of an anisotropic superconducting material. 
     
     
       4. The superconducting magnetic coil assembly of claim 3 wherein the first anisotropic superconductor is in the form of a superconductor tape. 
     
     
       5. The superconducting magnetic coil assembly of claim 4 wherein the first anisotropic superconductor tape is in a monolithic form. 
     
     
       6. The superconducting magnetic coil assembly of claim 5 wherein the monolithic-form first anisotropic superconductor tape is in the form of a monofilament superconductor. 
     
     
       7. The superconducting magnetic coil assembly of claim 5 wherein the monolithic-form first anisotropic superconductor tape includes a multifilament composite superconductor having individual superconducting filaments which extend the length of the multifilament composite superconductor. 
     
     
       8. The superconducting magnetic coil assembly of claim 7 wherein the first resistivity characteristic, in its normal state, is a range between about 10 to 50 μΩ-cm. 
     
     
       9. The superconducting magnetic coil assembly of claim 4 wherein the superconductor tape has an aspect ratio in a range between about 200:1 and 500:1. 
     
     
       10. The superconducting magnetic coil assembly of claim 4 wherein the superconductor tape includes a backing strip formed of a thermal stabilizer. 
     
     
       11. The superconducting magnetic coil assembly of claim 10 wherein the backing strip has a resistivity characteristic greater than about 10 μΩ-cm. 
     
     
       12. The superconducting magnetic coil assembly of claim 3 wherein the second anisotropic superconductor is formed as a superconductor tape. 
     
     
       13. The superconducting magnetic coil assembly of claim 12 wherein the superconductor tape of the second anisotropic superconductor includes a multifilament composite superconductor having individual superconducting filaments which extend the length of the multifilament composite superconductor and are surrounded by a matrix forming material. 
     
     
       14. The superconducting magnetic coil assembly of claim 13 wherein the individual superconducting filaments of the second anisotropic superconductor are twisted. 
     
     
       15. The superconducting magnetic coil assembly of claim 3 wherein the first superconductor is wound in a layered configuration. 
     
     
       16. The superconducting magnetic coil assembly of claim 3 wherein the first superconductor is formed of pancake coils each coil electrically connected to an adjacent coil. 
     
     
       17. The superconducting magnetic coil assembly of claim 16 wherein the first superconductor is formed of double pancake coils. 
     
     
       18. The superconducting magnetic coil assembly of claim 3 wherein the second superconductor is wound as a pancake coil. 
     
     
       19. The superconducting magnetic coil assembly of claim 15 wherein the second superconductor is wound as a pancake coil. 
     
     
       20. The superconducting magnetic coil assembly of claim 16 wherein the second anisotropic superconductor is wound as a pancake coil. 
     
     
       21. The superconducting magnetic coil assembly of claim 3 wherein a first segment of the first superconductor extends along the longitudinal axis in a first direction toward the second superconductor and connects to a first end of a first segment of the second superconductor at a first junction, a second end of the first segment connected to a second segment of the first superconductor, the second segment extending along the longitudinal axis in a second direction away from the second superconductor. 
     
     
       22. The superconducting magnetic coil assembly of claim 3 wherein the first and second superconductors are high temperature superconductors. 
     
     
       23. The superconducting magnetic coil assembly of claim 3 wherein the first superconductor constitutes greater than 50% of the total amount of superconductor of the coil. 
     
     
       24. The superconducting magnetic coil assembly of claim 3 wherein the second superconductor constitutes a portion of the total amount of superconductor of the coil in a range between 5% and 30%. 
     
     
       25. The superconducting magnetic coil assembly of claim 24 wherein the second superconductor constitutes about 10% of the total amount of superconductor of the coil. 
     
     
       26. A superconducting magnetic coil assembly having a center section and two end sections positioned along a longitudinal axis for generating a magnetic field that varies along the longitudinal axis of the coil assembly, the coil assembly comprising: a first anisotropic superconductor wound about the longitudinal axis of the coil assembly in a region of the center section and forming a first coil section, the first anisotropic superconductor formed as a superconducting tape having a wide surface and configured to provide, in a superconducting state, a low AC loss characteristic in the presence of magnetic fields parallel to the wide surface of the superconducting tape; and   a second superconductor, different from the first anisotropic superconductor and wound about the longitudinal axis of the coil assembly in a region of at least one of the end sections and forming at least one second coil, the second superconductor connected to an end of the first anisotropic superconductor and configured to provide, in a superconducting state, a low AC loss characteristic in the presence of magnetic fields parallel to the wide surface of the superconducting tape of the first superconductor, wherein the AC loss characteristic of the second superconductor is lower than the AC loss characteristic of the first superconductor.   
     
     
       27. The superconducting magnetic coil assembly of claim 26 wherein the second superconductor is formed of an anisotropic superconducting material. 
     
     
       28. The superconducting magnetic coil assembly of claim 27 wherein the first anisotropic superconductor is in a monolithic form. 
     
     
       29. The superconducting magnetic coil assembly of claim 28 wherein the monolithic-form first anisotropic superconductor is in the form of a monofilament superconductor. 
     
     
       30. The superconducting magnetic coil assembly of claim 28 wherein the monolithic-form first anisotropic superconductor tape includes a multifilament composite superconductor having individual superconducting filaments which extend the length of the multifilament composite superconductor. 
     
     
       31. The superconducting magnetic coil assembly of claim 30 wherein the multifilament composite superconductor has a resistivity characteristic, in its normal state, in a range between about 10 to 50 μΩ-cm. 
     
     
       32. The superconducting magnetic coil assembly of claim 26 wherein the superconducting tape has an aspect ratio in a range between about 200:1 and 500:1. 
     
     
       33. The superconducting magnetic coil assembly of claim 26 wherein the superconducting tape includes a backing strip formed of a thermal stabilizer. 
     
     
       34. The superconducting magnetic coil assembly of claim 33 wherein the backing strip has a resistivity characteristic greater than about 10 μΩ-cm. 
     
     
       35. The superconducting magnetic coil assembly of claim 26 wherein the second anisotropic superconductor is formed as a superconducting tape. 
     
     
       36. The superconducting magnetic coil assembly of claim 35 wherein the second superconductor includes a multifilament composite superconductor having individual superconducting filaments which extend the length of the multifilament composite superconductor and are surrounded by a matrix forming material. 
     
     
       37. The superconducting magnetic coil assembly of claim 36 wherein the individual superconducting filaments of the second anisotropic superconductor are twisted. 
     
     
       38. The superconducting magnetic coil assembly of claim 26 wherein the first anisotropic superconductor is wound in a layered configuration. 
     
     
       39. The superconducting magnetic coil assembly of claim 26 wherein the first anisotropic superconductor is formed of pancake coils each coil electrically connected to an adjacent coil. 
     
     
       40. The superconducting magnetic coil assembly of claim 39 wherein the first superconductor is formed of double pancake coils. 
     
     
       41. The superconducting magnetic coil assembly of claim 26 wherein the second superconductor is wound as a pancake coil. 
     
     
       42. The superconducting magnetic coil assembly of claim 38 wherein the second superconductor is wound as a pancake coil. 
     
     
       43. The superconducting magnetic coil assembly of claim 38 wherein the second superconductor is wound as a pancake coil. 
     
     
       44. The superconducting magnetic coil assembly of claim 26 wherein a first segment of the first superconductor extends along the longitudinal axis in a first direction toward the second superconductor and connects to a first end of a first segment of the second superconductor at a first junction, a second end of the first segment connected to a second segment of the first superconductor, the second segment extending along the longitudinal axis in a second direction away from the second superconductor. 
     
     
       45. The superconducting magnetic coil assembly of claim 26 wherein the first and second superconductors are high temperature superconductors. 
     
     
       46. The superconducting magnetic coil assembly of claim 26 wherein the first superconductor constitutes greater than 50% of the total amount of superconductor of the coil. 
     
     
       47. The superconducting magnetic coil assembly of claim 26 wherein the second superconductor constitutes a portion of the total amount of superconductor of the coil in a range between 5% and 30%. 
     
     
       48. The superconducting magnetic coil assembly of claim 47 herein the second superconductor constitutes about 10% of the total amount of superconductor of the coil. 
     
     
       49. A superconducting magnetic coil assembly generating a magnetic field that varies along a longitudinal axis, the coil assembly comprising: a center coil section wound about the longitudinal axis in a center region of the coil assembly and comprising a first anisotropic superconductor; and   at least one end coil section wound about the longitudinal axis in an end region of the coil assembly, said end coil section positioned proximate to the center coil section along the longitudinal axis and comprising a second superconductor different from said first anisotropic superconductor;   wherein said second superconductor has lower AC losses in the presence of a magnetic field oriented perpendicular to the longitudinal axis than said first anisotropic superconductor.